This disclosure relates to the field of file systems and storage systems that operate with file systems.
File systems are used by data processing systems to manage the storage of data, such as a user's data files and files for application programs (including executable software) and files for an operating system (including executable software). A file system maintains one or more data structures that allow it to keep track of where data is stored on a storage device, such as a magnetic hard drive. These data structures are used when a read request or a write request is made by, for example, an application program or one or more components of the operating system. File systems can also be used with a composite storage device that includes two types of storage devices that together are treated as a single logical storage volume. U.S. patent application Ser. No. 13/605,916, filed Sep. 6, 2012 (entitled: Data Migration For Composite Non-Volatile Storage Device) describes examples of composite storage devices, and this prior application is incorporated hereby by reference.